Track circuit apparatus



April 1940- H. A. THOMPSON T AL, 2,196,616 TRACK CIRCUIT APPARATUS Filed Sept. 27, 1959 722 1K- 7191 ad INVENTORS, HowardAT flfOIZ and Patented A r. 9, 1940 -'UNI-TED; STATE,S.

'raAoK CIRCUIT APPARATUS Howard A. Thompson and George W. Bau gh man, 7

. Edgewood, Pa., assignors to The Union Switch & Signal Company, Swissvale, Pa., a co'rpora- I "tion of Pennsylvania 'Applicat ion September 27, 1939, Serial na zseeso 4 Claims. (01. 246-34) inate the'necessi'ty for using polarized or two- 1 position track relays and stzngg'ering the :polarity of adjoining track circuits; to avoid false relay operation. Afur'ther. object is to'provide a path t for the fiow of propulsion current around the insulated rail joints withoutintroducing any dead sections of track rinwhich' the presence of a car could not b'edetecte'd. Other objects and advantageswill becomeblear as'the descri'p'; I I I "f joints '12a, 2 b,]2c, and Zd'tdforni'two adjoining track circuit sections A-Carid CE; Each of tion progresses. '3 v I We shall describe one form of apparatus em bodying our invention and shall then point out I employing alternating current track circuits.

In railway signaling track circuits, provision must 'be made against fals'efenergizationfof the track relays due to leakage of current'irom adv joining track circuitsover rail jointsin 1 which the insulation has been broken down. In general, this'false energization can be prevented by using polarized or two-element track relays and stag gering the polarity in adjoining track circuits so that theleakage current will cause .a'reversal or deenergization Qf the afiectedi track relay, Where alternating current ftrack circu-its are employed, the use of two-element; trackrelaysj presentsa problem due to the 'factthat when'the transmission line I is sectionalized, one element of the track relay 'at the sectionalizi'ng location may. receive current from 'one source of supply while the other element receives its-venergy"frorri"a difierent source, thusr'endering the relay inoperative. Accordingly; difiiculties areencountered with two-element alternating current relays .rent around the various insulated rail joints. For

I where sectionalizing must be employed. I II I The apparatus embodying our. invention does not require a twoeelement track relay and" provide's broken down insulated, rail joint protecp tion in any alternating current track circuit;

whether on a steam road or in electric propulsion territory. The insulated rail joints which we employ may be of the usual type but these are so arranged short insulated section. of track andwith certain inductances connected across the rails at the rail joint'locationsthat in the event of breakdown of the insulation, the failure will 'be indicated I v by a release of the associated track relay;

PATENT in conjunction-math a'relatively' Y The foregoing protectionis obtaineddue to the factthat a-failure 0f thein'sulationat the rail joint will short-circuit a portion of the inductance which is c'o nnected across 'therails, thus partly short-circuitinjg the track circuit, Accordingly; our invention permits the use of single element track relays energized from an alternating current track circuit, andfelimin'ates the transmission line sectionalizing problem without sacrificingbroken-down rail joint protection. I Referring now to the 'drawing,'the referencecharacters I and la designate the two rails of a stretch of trackdivided' by the insulated rail through a suitablecurrent limiting impedance X. Each track transformerIisenergized from a suitable {source of alternating current (not showmahavi'ng the terminals BX-CX. The signal S at location C'is controlled over the contacts same location, inthe' usual'manner. The ,partic- I ular'control circuits for-this signalare well known and have not been; shown in detail in order to simplifythe disclosure. I

It will be noted that we make wherelthe twoftrackjsectionjs 'A--C and C E adjoin for a purpose which will become clear the description progresses. These rail sections may represent astand'ard rail length such," for example; as 32 rear and"there'fore do not ordinarily require any cutting'o f theraih The impedance bonds IB and IBI as welli'as the connectors l2; [4- and'l5 are provided for the'pu'rpose'o'i establishing a path for thefiovv of propulsion cursection |0, wire l2,'rail section ll; wire l5, and f upper half 5 of the impedance bond IBI, to the upper rail l.-, Similarly, propulsion current flowing in the lower rail la'rnaytake a path through the lower portion 4 of impedance bond 13, wire I4,'rail section HL'wire l2, rail section II, Wire l5, and lower half 6 of the impedance bond IBi, to the lower rail la. Since the propulsion currentflows' in opposite directions in the two halves of each impedance bond, the induction eifects due to the propulsion current are substantially neutralized so that no appreciable propulsion potential is impressed across the two rails of the track.

The track circuit current flows from the track transformer to the respective track relay in the usual manner, it being observed, however, that the rail sections In and l I do notreceive any track circuit current. Dueto the arrangement of the v apparatus, the rail lengths liland H do not represent dead sections of track but, on the contrary, are responsive to the presenceof a train or car either partly or wholly within the section B--D. The rail joints 2b and may be located approximately opposite one another whereas the joints Za'and 2d are preferably: staggered, one to the left and the other to the right of the rail joints at the signal location With the foregoing arrangement, should a car stand wholly between the rail joints 2a and 2b, for example, the car will obviously place a shortcircuit upon the upper halffi of the impedance bond 13," thus partly short-circuiting the track circuit so that relay TR will remain released. Similar1y,1if the car is wholly between'the rail joints 2c and'Zd, it will short-circuit the lower intr -rail voltage in theformer two sections is about one-half of thateffectivein the latter sections. This shunting sensitivity is, however, adequate for satisfactory operationflin practice.

A failure of either rail joint 2a or 2d'will. ob- I viously short-circuit the respective winding 4 or 5 of the associated impedancebond'IB or vIBi, whereupon the track circuit voltage will be reduced to practically zero and the fault will accordinglybe indicated by a release of the respective track relay even though the, track is unoccupied at the time; Similarly, a failure of ither rail joint 2b or 20 will place a short-circuit a on the respective winding 3 or G of the asso:

ciated impedance bond, thereby also causing a release of the trackrelay for the associated section. On the other hand, a break in any of the connectors l4, l2, andtlg'i or in therails l0 and H will be evidenced by a partial or total'interruption of the propulsion current. I From the foregoing, it will be apparent thatfwe have provided track circuit apparatus which effectively eliminatesthe danger arising from a failureof .the insulated rail joints in .a simple and safe manner. I

Although we have herein shown and described only one form of track circuit a'pparatus'embody-, ing our invention, it is understood that various Having thus described our invention, what we claim is: I '1'. In combination, a stretch of railway track divided into two trackcircuit sections by means of an intermediate portion of track separated from both said sections by insulated rail joints, a source of alternating current connectedacross the rails of one said section, a track relay connected across the rails of the other said section,

. an impedance bond for each'of said sections connected across therails of its respective section, a connection-from the mid-point of one impedance bond to onerail of said intermediate track portion, a connection from the mid-point of the other impedance bond to the other rail of said intermediate. track portion, and a connection joining the portion;

2. In; combination, a stretch of railway track, a first insulated rail joint in one rail of said track, a second insulatedv rail joint in the other rail of two rails of said'intermediate track I saidgtrack approximately opposite said first insecond track circuit to the right of said second insulated I rail joint and terminated thereby, a

source of alternating current for said first track circuit, a track relay for said second track circuit, a first and a second reactorconnected respectively across the rails of said first and said second track circuit, a connection from the midpoint of said first reactor to said second railportion, a connection from the mid-point of said second reactor to said first rail portion, and a connection joining said first and said second rail portions. I e I 3. In combination,astretch of railway track divided into two track circuit sections by means I of an intermediate portion of track separated from both said sectionsby insulated rail joints,

the two rails of said intermediate vtrack portion being staggered with respect to each other, a source ofalternating currentifor one of said sections, a track relayfor'the other of said sections;

a reactor for each ofsaid sections connected across the rails of its respective section, a connection fromthe mid-point of one reactor toone rail of said intermediatetrack portion, a con.- nection from the mid-point of the other=reactor to theother rail of saidintermediate track portion, and a connection joining the two rails of said intermediate track portion. I I

4. In combination, a stretch of railwaytrack divided'in to two track circuit sections by means.

of an intermediate portion oftrack separated from both said sections by insulated rail joints, the two rails of said intermediate track portion being staggered with respect to each other, a

track transformer having its secondary winding connected acrossthe rails of one of said sections, a current-limiting device'included in the connection ofsaid secondary winding, a track relay connected across the rails of the other of said sections, a reactor for each of, said sections connectedacross the rails of its respective section, a connection from the mid-point of; one reactor to one rail of said intermediate track portion, a connection from the mid-point of the other reactor to the other rail of said intermediate track portion, and a connection joining the tworails of saidintermediate track portion. I

' HOWARD A. THOMPSON.-

GEORGE .W. BAUGHMAN. 

